Question: At Simba Travel Agency, the price of a climbing trip to Mount Kilimanjaro includes an initial fee plus a constant fee per meter. The variable $f$ models the fee (in dollars) for climbing $d$ meters. $f=110+0.12d$ What is the initial fee? $\$$
Answer: Before the travel agency charges for any actual climbing, the distance climbed, $d$, is $0$, and the total fee is equal to the initial fee. We can calculate the fee: $\begin{aligned} f&=110+0.12d\\\\ f&=110+0.12(0) \\\\ f&=110+0 \\\\ f &= 110 \end{aligned}$ The initial fee is $\$110$.